I finally got it working! All you need to do is answer 'y' to 'use external agp gart module' when running fglrxconfig. I now get an error message involving my keyboard settings when I load gnome and my graphics card is still a 'VESA driver (generic)' in the display settings, but running glxinfo shows the radeon module is loaded and I am 3000 odd fps in glxgears. Woohoo!
To get the ATI Control program working, type
ln -s /usr/lib/libpng12.so.0 /usr/lib/libpng10.so.0
as root in a console window.
Let me know if anyone gets the same error message and if anyone knows how to resolve it.